IN BORNEAN FORESTS [chap. 



The luminosity of the ground in the forest and the phosphores- 

 cent insects flying about tempt to long digressions, the subject 

 being a highly suggestive one. So far as regards their biological 

 relations with other beings, luminous mushrooms probably do not 

 derive any advantage from the light-emitting property they possess. 

 It is merely the manifestation of a chemico-vital phenomenon, 

 which accidentally becomes so marked as to be visible. 



The case is very different with the fireflies, for in them the 

 phosphorescence ensures the meeting of the two sexes, and evidently 

 the phenomenon takes place under the stimulus of the reproductive 

 cells. That sentiment which is expressed by the word " love" im- 

 pelled the dark and invisible progenitors of the firefly to 

 render themselves as dazzling as the moon and the stars, the only 

 luminous objects with which their nocturnal habits made them 

 acquainted. It is well known how nocturnal insects are fascinated, 

 one might even say hypnotised, by light. And such must have 

 been the case also, and perhaps to a greater extent, in the remotest 

 plasmative epoch, when living beings, through processes as yet 

 mysterious to us, assumed the forms they now have. In this con- 

 nection, according to an hypothesis which I have long ago expressed 

 in a different form, I incline to the belief that the luminous organ 

 of fireflies, placed in the terminal abdominal segments of the body, 

 is the result of a kind of reproduction of luminous impressions 

 received through the eyes, and may thus be regarded as a 

 special form of mimicry. 



In the same way, I do not think it impossible that the attraction 

 for luminous and glittering objects may have been the prima causa 

 of the production of luminous spots and metallic or iridescent colours 

 in many beetles and butterflies. Thus, the golden green of Buprestis 

 reproduces, possibly, the shiny surfaces of leaves in strong light, 

 on which they love to rest ; and the mother-of-pearl spots on the 

 wings of some butterflies might find an explanation in the fascination 

 which reflected sunlight on a pool of water has for them. Phos- 

 phorescence and mimetic luminosity would thus in insects have 

 been derived from a common cause ; but in nocturnal insects, 

 in whom the colour of the external portion of the body 

 cannot have originated any ambitious sentiment, the physiological 

 process which has rendered luminous phenomena possible has 

 shown its effects internally ; whilst in the others its manifestation 

 is on the external surface of the body. 



Whilst my men worked at the construction of the house I 

 wandered about in the forest, or searched for insects amidst the 

 branches of the trees we had felled, which retained their freshness 

 for several days on account of the great dampness. Where a ray 

 of sun lighted their shining foliage I was sure to find some kind of 

 brilliant beetle with resplendent elytra; But on the ground, except 



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